[libc-commits] [libc] Reapply "[libc] build with -Werror (#73966)" (PR #74506)

[via libc-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Nick Desaulniers (nickdesaulniers)

<details>
<summary>Changes</summary>

This reverts commit 6886a52d6dbefff77f33de12ff85d654e2557f81.

Most of the errors observed in postsubmit have been addressed. We can
fix-forward the remaining ones.

Link: https://lab.llvm.org/buildbot/#/changes/117129


---
Full diff: https://github.com/llvm/llvm-project/pull/74506.diff


2 Files Affected:

- (modified) libc/cmake/modules/LLVMLibCObjectRules.cmake (+4) 
- (modified) libc/docs/dev/code_style.rst (+8) 


``````````diff
diff --git a/libc/cmake/modules/LLVMLibCObjectRules.cmake b/libc/cmake/modules/LLVMLibCObjectRules.cmake
index 5fbbfd58db2d0..ef654bd7b34ab 100644
--- a/libc/cmake/modules/LLVMLibCObjectRules.cmake
+++ b/libc/cmake/modules/LLVMLibCObjectRules.cmake
@@ -43,6 +43,10 @@ function(_get_common_compile_options output_var flags)
     list(APPEND compile_options "-fno-rtti")
     list(APPEND compile_options "-Wall")
     list(APPEND compile_options "-Wextra")
+    # -DLIBC_WNO_ERROR=ON if you can't build cleanly with -Werror.
+    if(NOT LIBC_WNO_ERROR)
+      list(APPEND compile_options "-Werror")
+    endif()
     list(APPEND compile_options "-Wconversion")
     list(APPEND compile_options "-Wno-sign-conversion")
     list(APPEND compile_options "-Wimplicit-fallthrough")
diff --git a/libc/docs/dev/code_style.rst b/libc/docs/dev/code_style.rst
index a050a4c1d3dd7..eeeced0359adb 100644
--- a/libc/docs/dev/code_style.rst
+++ b/libc/docs/dev/code_style.rst
@@ -178,3 +178,11 @@ these functions do not call the constructors and destructors of the
 allocated/deallocated objects. So, use these functions carefully and only
 when it is absolutely clear that constructor and destructor invocation is
 not required.
+
+Warnings in sources
+===================
+
+We expect contributions to be free of warnings from the `minimum supported
+compiler versions`__ (and newer).
+
+.. __: https://libc.llvm.org/compiler_support.html#minimum-supported-versions

``````````

</details>


https://github.com/llvm/llvm-project/pull/74506